Inhibitory effect of CP-1 and PD98059 on MSP or MSP plus TGF-β1-induced RSK2 phosphorylation: M-RON cells (3 × 106 cells per dish) in DMEM with 1% of FBS were first treated with CP-1 or PD98059 for 10 min followed by stimulation with MSP (2 nM) or MSP plus TGF-β1 (5 ng/ml). Cells were collected 30 min after stimulation. Phosphorylated RON was determined by Western blot analysis after Zt/g4 immunoprecipitation of cell lysates (250 μg proteins/sample). Phosphorylated Erk1/2 and RSK2 were directly determined by Western blot analysis using specific antibodies, respectively. Membranes were also reprobed with individual antibodies to detect non-phosphorylated proteins as the loading controls. Data shown here are from one of two experiments with similar results.